The spread of a digital camera is remarkable. The digital camera converts an object image into an electric signal by an electronic device such as a CCD (Charge Coupled Device), for example, and stores the converted electric signal in a memory. Further, recently, an information terminal device on which a digital camera is mounted, such as a cellular phone, a smartphone, or a tablet terminal is also spreaded widely.
A dynamic range of an imaging device used in a digital camera or the like is very narrow compared with a film. Therefore, so-called underexposure (or black spot) or overexposure (or white spot) occurs depending upon an imaging condition, whereby image quality is extremely deteriorated. In order to solve such a defect, an HDR synthesize function gains attention. In the HDR synthesize function, a plurality of images is taken while changing exposure, dark portions are extracted from an image obtained by lengthening exposure and bright portions are extracted from an image obtained by shortening exposure when these images are to be synthesized, whereby a broad dynamic range can be acquired while suppressing overexposure and underexposure.
For example, Patent document 1 discloses a video generating apparatus that has two imaging devices in which one with high resolution takes an image with a small exposure amount and the other with low resolution takes an image with a large exposure amount for a short exposure time, whereby an HDR synthetic image is created while reducing noise due to camera shake or the like.